Well they usually give us 5-15 minutes. Sometimes it shuts down by itself and there is nothing they can do. A few weeks ago they had it down for over 12 hours because of a storm that took out the power from the hosting company. They can't always control everything, ya know?

We try and not email blast our entire user base too often. It's a push and pull though, because sometimes we want to announce things but not annoy people. Also, sometimes, like becca put so eloquently, we just don't know when bad things are gonna happen. Generally these outages are pretty quick (5-15 minutes), but for anything worse we try to announce wherever possible: facebook, twitter, and the main site. I'm guessing you're probably seeing the 'connection lost' message due to poor site performance, which we are definitely trying to fix that up. @shadowfiend has some fresh goodness he's been working on to solve this.
and @hero, we only use Flash on our standalone Invite page and that's only for the "copy to clipboard" functionality. Flash shouldn't cause any issues on our main page :/